Environmental antibiotic resistance genes (ARGs) have received much attention, while the characteristics of ARGs carried by particulate matter (PM) as a function of urban functional region are almost unknown. In this study, ARGs carried by PM2.5 and PM10 in an urban hospital, a nearby urban community and the nearest suburban community were detected using metagenomics. In total, 643 ARG subtypes belonging to 22 different ARG types were identified. The chloramphenicol exporter gene, sul1, bacA, and lnuA were the most abundant ARG subtypes in all air samples. The hospital exhibited higher ARG abundance and richness than the nearby communities. ARG profiles depended on functional region: hospital and suburban samples clustered separately, and samples from the nearby urban community interspersed among them. The representation of multidrug and quinolone resistance genes decayed with distance from the hospital to the urban community to the suburban community, indicating that hospital PM may be a hotspot for ARGs encoding proteins conferring multidrug and quinolone resistance. Airborne ARGs carried by PM in the hospital environment were more closely associated with clinically important pathogens than were those in nearby communities. In particular, carbapenemase genes, including blaNDM,blaKPC,blaIMP,blaVIM,and blaOXA-48, were discovered in hospital PM. In the suburban community, crAssphage, a human host-specific bacteriophage, was applied to predict ARG abundance and found to be enriched due to anthropogenic pollution but showed no clear evidence for ARG selection. In the hospital and the nearby urban community, the drivers of ARGs were complex. Our results highlighted that PM ARGs were closely related to human activities and revealed a potential hotspot, which could provide new evidence for further research and consequently mitigate the formation of airborne ARGs and transfer risks.
Exposure to the indoor airborne microbiome is closely related to the air that individuals breathe. However, the floor dust-borne microbiome is commonly used as a proxy for indoor airborne microbiome, and the spatial distribution of indoor airborne microbiome is less well understood. This study aimed to characterize indoor airborne microorganisms at varying heights and compare them with those in floor dust. An assembly of three horizontally and three vertically positioned Petri dishes coated with mineral oil was applied for passive air sampling continuously at three heights without interruption. The airborne microbiomes at the three different heights showed slight stratification and differed significantly from those found in the floor dust. Based on the apportionment results from the fast expectation-maximization algorithm (FEAST), shoe sole dust contributed approximately 4% to indoor airborne bacteria and 14% to airborne fungi, a contribution that is comparable to that from the floor dust-borne microbiome. The results indicated that floor dust may not be a reliable proxy for indoor airborne microbiome. Moreover, the study highlights the need for height-resolved studies of indoor airborne microbiomes among humans in different activity modes and life states. Additionally, shoe sole-dust-associated microorganisms could potentially be a source to "re-wild" the indoor microbiota.
Numerous threats from biological aerosol exposures, such as those from H1N1 influenza, SARS, bird flu, and bioterrorism activities necessitate the development of a real-time bioaerosol sensing system, which however is a long-standing challenge in the field. Here, we developed a real-time monitoring system for airborne influenza H3N2 viruses by integrating electronically addressable silicon nanowire (SiNW) sensor devices, microfluidics and bioaerosol-to-hydrosol air sampling techniques. When airborne influenza H3N2 virus samples were collected and delivered to antibody-modified SiNW devices, discrete nanowire conductance changes were observed within seconds. In contrast, the conductance levels remained relatively unchanged when indoor air or clean air samples were delivered. A 10-fold increase in virus concentration was found to give rise to about 20-30% increase in the sensor response. The selectivity of the sensing device was successfully demonstrated using H1N1 viruses and house dust allergens. From the simulated aerosol release to the detection, we observed a time scale of 1-2 min. Quantitative polymerase chain reaction (qPCR) tests revealed that higher virus concentrations in the air samples generally corresponded to higher conductance levels in the SiNW devices. In addition, the display of detection data on remote platforms such as cell phone and computer was also successfully demonstrated with a wireless module. The work here is expected to lead to innovative methods for biological aerosol monitoring, and further improvements in each of the integrated elements could extend the system to real world applications.
Exhaled breath condensate (EBC) is increasingly being used as a non-invasive method for disease diagnosis and environmental exposure assessment. By using hydrophobic surface, ice, and droplet scavenging, a simple impaction and condensing based collection method is reported here. Human subjects were recruited to exhale toward the device for 1, 2, 3, and 4 min. The exhaled breath quickly formed into tiny droplets on the hydrophobic surface, which were subsequently scavenged into a 10 µL rolling deionized water droplet. The collected EBC was further analyzed using culturing, DNA stain, Scanning Electron Microscope (SEM), polymerase chain reaction (PCR) and colorimetry (VITEK 2) for bacteria and viruses. Experimental data revealed that bacteria and viruses in EBC can be rapidly collected using the method developed here, with an observed efficiency of 100 µL EBC within 1 min. Culturing, DNA stain, SEM, and qPCR methods all detected high bacterial concentrations up to 7000 CFU/m3 in exhaled breath, including both viable and dead cells of various types. Sphingomonas paucimobilis and Kocuria variants were found dominant in EBC samples using VITEK 2 system. SEM images revealed that most bacteria in exhaled breath are detected in the size range of 0.5–1.0 µm, which is able to enable them to remain airborne for a longer time, thus presenting a risk for airborne transmission of potential diseases. Using qPCR, influenza A H3N2 viruses were also detected in one EBC sample. Different from other devices restricted solely to condensation, the developed method can be easily achieved both by impaction and condensation in a laboratory and could impact current practice of EBC collection. Nonetheless, the reported work is a proof-of-concept demonstration, and its performance in non-invasive disease diagnosis such as bacterimia and virus infections needs to be further validated including effects of its influencing matrix.
Poor air hygiene as a result of bioaerosol contamination has caused diverse forms of adverse health effects and diseases. In addition, global biosecurity is threatened by purposeful use of biowarfare agents and the vulnerability of people to the infectious agents. Accordingly, developments in high-volume biosampling, including aerosol-to-hydrosol techniques with low cut-off size, real-time bioaerosol detection, adequate biological quantification, and exposure control, as well as the investigation of the link between disease outcome and bioaerosol exposure, are current areas of bioaerosol research. Although milestone progress has been achieved both in bioaerosol sampling and analysis techniques since late 1800s, compared to atmospheric chemistry the bioaerosol field is still understudied. This is partially because of the lack of both bioaerosol scientists and multidisciplinary collaboration. It is becoming necessary to develop a pool of scientists with different expertise, e.g., bioaerosol scientists, environmental engineers, biomedical engineers, epidemiologists, microbiologists, chemists, physicists, as well as researchers in other engineering fields, in mitigating bioaerosol-related adverse health effects, eliminating diseases, and preventing and controlling epidemic outbreaks. This work is conducted to broadly review current state-of-the-art sciences and technologies in the bioaerosol field. In tackling the challenges ahead, the review also provides perspectives for bioaerosol research needs, and further reminds bioaerosol scientists of those existing technologies in other fields that can be leveraged. In view of the past, forward-looking hypotheses and revolutional perspectives are needed to be formed in order to allow the bioaerosol research have major impacts in the academic community in this new millennium.
Stand-alone portable air purifiers (APs) have become an increasingly popular method of controlling individual inhalation exposure. Exposure to bacterial endotoxins has a causative role in respiratory inhalation health. Here, we studied the changes in endotoxin levels in indoor air before and after purification by a portable AP equipped with HEPA (high-efficiency particulate air) filters. An increase in endotoxins was observed when a previously used AP was turned on to clean the air. Replacing the HEPA filters in the AP helped to mitigate the increase in endotoxins of larger sizes but not endotoxins of smaller sizes. Consequently, the use of APs could lead to increased endotoxin deposition in airways, especially in the alveolar region. The endotoxin concentrations on the HEPA filters were well correlated with the free DNA concentrations on the HEPA filters. This correlation indicates that the disrupted bacteria, which released free DNA, could also release endotoxins, thus making HEPA filters a source of indoor airborne endotoxins. Our results illustrate a potential endotoxin inhalation risk associated with HEPA-APs as an air cleaning strategy and highlight the importance of composition-specific air cleaning while reducing the particle number/mass.
At 14:28 on 12 May 2008, Sichuan Province of China suffered a devastating earthquake measuring 8.0 on the Richter scale with more than 80 000 human lives lost and millions displaced. With inadequate shelter, poor access to health services, and disrupted ecology, the survivors were at enormous risk of infectious disease outbreaks. This work, believed to be unprecedented, was carried out to contain a possible outbreak through onsite monitoring of airborne biological agents in the high-risk areas. In such a mission, a mobile laboratory was developed using a customized vehicle along with state-of-art bioaerosol and molecular equipment and tools, and deployed to Sichuan 11 days after the earthquake. Using a high volume bioaerosol sampler (RCS High Flow) and Button Inhalable Aerosol Sampler equipped with gelatin filters, a total of 55 air samples, among which are 28 filter samples, were collected from rubble, medical centers, and camps of refugees, troops and rescue workers between 23 May and 9 June, 2008. After pre-treatment of the air samples, quantitative polymerase chain reaction (qPCR), gel electrophoresis, limulus amebocyte lysate (LAL) assay and enzyme-linked immunosorbent assay (ELISA) were applied to detect infectious agents and to quantify environmental toxins and allergens. The results revealed that, while high levels of endotoxin (180∼975 ng/m3) and (1,3)-β-D-glucans (11∼100 ng/m3) were observed, infectious agents such as Bacillus anthracis, Bordetella pertussis, Neisseria meningitidis, Mycobacterium tuberculosis, influenza A virus, bird flu virus (H5N1), enteric viruses, and Meningococcal meningitis were found below their detection limits. The total bacterial concentrations were found to range from 250 to 2.5 × 105DNA copies/L. Aspergillus fumigatus (Asp f 1) and dust mite allergens (Der p 1 and Der f 1) were also found below their detection limits.
Some specific spoilage organisms (SSO) respond to the presence of exogenous N-acyl-homoserine lactones (AHLs) through the quorum sensing (QS) system to modulate their spoilage characteristics. To explore the effect of exogenous AHLs on the spoilage characteristics of Pseudomonas koreensis PS1 from spoiled chilled pork, four kinds of AHLs were added to the liquid medium to analyze their effect on the cell growth and spoilage characteristics of P. koreensis PS1, and N-hexanoyl-l-homoserine lactone (C6-HSL) was added to evaluate its effect on spoilage characteristics of P. koreensis PS1 inoculated in fresh chilled pork. The results showed that the addition of low concentrations of C6-HSL (10 µmol/L) to the liquid medium could remarkably promote the protease activity, lipase activity, and biofilm formation of P. koreensis PS1 (p < 0.05), and more than 30 µmol/L C6-HSL could significantly increase the cell density (p < 0.05). Furthermore, the addition of 10 µmol/L C6-HSL into fresh chilled pork could increase the lipase and protease activities of P. koreensis PS1. The enzyme activity accelerated the decomposition of total protein, total fat, and total sugar, and led to an increase in putrescine, tyramine, cadaverine, and total volatile basic nitrogen (TVB-N) content in chilled pork during the storage at 4°C. PRACTICAL APPLICATION: The infestation of chilled pork with SSO may be a challenge for the meat industry. In this study, exogenous AHLs were found to have a positive effect on the spoilage of chilled pork. The elimination of the QS phenomenon of bacteria should be considered when looking for ways to prolong the preservation of chilled pork.
Preventing adverse events due to unstable oxygen saturation (SpO2) at night in pregnant women is of utmost importance. Poor sleep has been demonstrated to impact SpO2 levels. Nowadays, many gravida have a habit of prolonged exposure to light before sleep, which can disrupt their sleep. Therefore, this study aimed at investigate the relationship between lights-out time, sleep parameters and SpO2, exploring the underlying mechanisms.
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